There are many devices that either produce variable low voltage DC power (below 100 VDC) or require low voltage DC power. A common example of a low voltage DC power source is a fuel cell, which is an electrochemical device which reacts hydrogen with oxygen to produce electricity and water. The basic process is highly efficient, and fuel cells fueled directly by hydrogen are substantially pollution free. Yet, the output of fuel cells (variable low voltage, high current DC power) makes efficient engineering solutions difficult, especially in residential and light commercial applications, where the power output demands of a fuel cell are not as significant. While sophisticated balance-of-plant systems are used for optimizing and maintaining relatively low power capacity applications, they do not effectively meet residential and light commercial power needs and at least a portion of this failure is attributable to the lack of effective power electronics to pair with low voltage DC power sources and loads.
For some low voltage DC sources such as fuel cells and batteries, the power conversion efficiency degrades over time as the sources are depleted. For example, for fuel cells, the fuel cell stack produces variable low-voltage DC based on power demand and the stack's average voltage degrades over time based on catalyst loss and energy conversion efficiency degradation. Increasing the number of fuel cells running in parallel will increase the output stack voltage, but degradation will still render the system inefficient and possibly unusable in a relatively short amount of time, requiring that the fuel cell stack be replaced.